Neighbours had alerted police and activists after they heard the girl crying and screaming for help from the balcony.

'Never seen such violence'

In the latest case, the victim, a tribal from the eastern state of Jharkhand, was rescued from South Delhi's Vasant Kunj area on Monday evening and taken to hospital with severe injuries on her face, head and back, the BBC Hindi's Faisal Mohammad Ali reports.

"In years of rescuing girls or children I have never seen such violence," Rishi Kant from the anti-trafficking group Shakti Vahini told the BBC.

"There was severe head injury, we could see some kind of bite marks on her body, we immediately rushed her to the hospital as we feared that she may develop some infection," he said.